Traditionally, open loop variable flow source systems that attempt to meter flow directly through varying the output of the variable flow source do not provide sufficient flow rate accuracy for most applications. Typically, to provide the required accuracy, a closed loop system that controls the output of the variable flow source based on metered flow rate is required. The closed loop system typically includes a fuel metering valve located downstream of the variable flow source. The fuel metering valve is selectively positioned to restrict fuel flow in the downstream manifold to provide a metered flow rate of pressurized fuel to the combustion chamber of an engine. With such a fuel metering system, a separate pressure regulation system may be used to maintain a substantially constant differential pressure across the fuel metering valve. Moreover, the fuel metering system may include a separate shutoff valve to block fuel flow to the engine combustion chamber during a shutoff operation.
By reducing the number of components in the fuel metering system, the cost and weight of the system may be substantially reduced and system reliability may be substantially increased. In addition, a system capable of measuring the flow rate of pressurized fuel provided to the engine combustion chamber and providing this as closed loop feedback to a controller that controls the output of the variable flow source, allows for precise control of the metered flow rate.